This is a Leatherjacket grub which eats the roots of the grass resulting in brown patches. Leatherjackets are the larvae of crane flies (Diptera: Tipulidae). The vast majority of the species in this very large family are completely harmless however these turf pests are among the very few exceptions. In the late summer and early fall you will see Crane Flies (daddy long legs) flying or skipping along your lawn laying eggs which develop into the grubs.  A large population can totally destroy your lawn but in Ontario it is against the law to spray pesticides to kill them.  More information on this web site: http://info.plantmenow.co.uk/leatherjacket/610/   Raccoons and skunks will sometimes pull up the sod to eat the grubs and birds will peck through the grass to feed on them.